Determining When to Plant

The question of when to plant your vegetables, especially
tomatoes and their eggplant cousins, out in the garden is the number one
question new gardeners have.

First read all the information included on the seed package or transplant label. Next, determine your
Plant Hardiness Zone and dates of average last frost or first freeze.

Take into consideration the micro climate of your garden. Is it very protected and warms up early? Is it exposed to prevailing winds that cool the area? Do you have areas of pavers or asphalt that keep the area warm? You may want to consult with your neighbors.

Last, use your best judgment. Read the 2 examples below for guidance. They are based on 2009 dates.

Example 1

Let's say I live in Hardiness Zone 5 near Matamoras, Pike county. Today is May 8th, 2009 and I want to plant my tomato plants outside in the garden. Assume I have already completed the hardening off process.

Will they be safe from frost? If I follow the Lunar Calendar or Gardening by the Moon philosophy, I need to wait until after the
Full Flower Moon. This occurs on May 9th this year. That's tomorrow, YEAH.

If I follow the more conventional Average Date of Last Frost philosophy, I can check the US National Climate Data Center Freeze - Frost Map
and determine that my average date of last frost falls between May 15 - June 1. Well that's a bit of a large time frame.

How about the US Chart method of determining my average date of last frost.
NCDC Freeze - Frost Chart I click on my state and then find the city nearest to me in the chart. Ok here is Matamoras.

According to the chart there is a 50% probability of a temperature below 32° after May 4, but only a 10% probability of a temperature below 32° after May 18. That's a little better.

Now what does NOAA or the Weather Channel say the temperature trend will be for the next 10 days? Enter your zipcode into the search box at the top of the page at the
Weather Channel's website You should see the 10-Day button on the right (below the top banner).

Well it seems that I need to rely on my experience just as much as what a chart or website tells me. I can always take the chance of planting them May 9 but also have a backup plan in the form of black mulch paper and floating row covers, wall o' waters or a mini greenhouse cover.

Example 2

Let's say that it's now July 20 and I want to plant a crop of spinach for fall harvesting. The package says to sow seeds directly in the garden 6 weeks before my average date of first frost (freeze date).

Back to the US Map.
It shows the average date of first fall frost falls between Sept 1 - Sept 15.

What about the
US Chart? It shows only a 10% probability of a temperature below 32° before September 26.

Either way it appears that if I plant my spinach now I should be able to harvest my crop before it freezes.

What's the Answer?

After checking all available information, I have determined that there is no definative answer to the when to plant question out there.

If you choose to rely on someone who says "oh you live in Weatherly? Plant your tomatoes on May 11th;" or a website that asks for your zipcode and gives you a precise answer, that is your decision to make.

But remember, they don't know your garden's climate like you do. You are the best judge of your garden.